CN105938931A - Balanced unbalanced transformer and design method thereof - Google Patents

Abstract

The invention relates to a balanced unbalanced transformer. The balanced unbalanced transformer comprises a coplanar waveguide power divider of a concentric structure; the power divider adopts a two-stage cascade form, and is formed by cascading two coplanar waveguides of concentric structures using Rogers 4350B as a base material; each concentric structure consists of an inner ring path line, a center path line and an outer ring path line from inside to outside in sequence; and each inner ring path line is electrically connected with the corresponding outer ring path line. According to the balanced unbalanced transformer disclosed by the invention, the available bandwidth is relatively wide, and all S parameters are easy to measure; and meanwhile, the balanced unbalanced transformer has better port isolation characteristic in a relatively wide frequency band range, and also has a relatively ideal phase characteristic.

Description

A kind of balun and method for designing thereof

Technical field

The present invention relates to balun, particularly to a kind of wideband balance imbalance converter and design side thereof Method.

Background technology

Balun (Balun) is balancedunbalanced converter, is the important devices that single-ended signal is converted into double-end signal.Bar Human relations can not only play good impedance matching effect, and at balancing antenna feeding network, microwave equilibration frequency mixer and push away Draw in the multiple microwave radio devices such as amplifier and there is important effect.Such as in Antenna Design, have dipole structure (or Can equivalence become dipole structure) symmetrical antenna, it is desirable to the electric current of feed antenna be balance.If feed-in current imbalance The characteristics such as the directional diagram of antenna, polarization mode will be caused to change so that the performance of antenna reduces.Especially in wider frequency The symmetrical antenna used in band has higher requirement to feeding network.

Balun is for realizing the signal conversion of single-end circuit and double end converter.Single-end circuit i.e. impedance transformer, wave filter Etc single ended input or Single-end output circuit, the signal of transmission is non-equilibrium signal；Double end converter is balanced mixer, symmetry The double-width grinding circuit of a period of time antenna etc, transmission is balanced signal.

A lot of balun of the prior art otherwise can test easily its whole S parameter (balancing device hybrid guided mode scatter Parameter), but bandwidth is less；Broader bandwidth, is but difficult to measure its whole S parameter.

Summary of the invention

In view of the above problems, it is proposed that the present invention, in order on offer one overcomes the problems referred to above or solves at least in part State a kind of balun of problem.

According to an aspect of the present invention, it is provided that a kind of balun, including concentric structure co-planar waveguide merit Point device, described power splitter uses two-stage cascade form, by two concentric structures, coplanar ripple with Rogers 4350B as base material Leading cascade to form, each concentric structure is made up of internal ring path, central trace and outer shroud path the most successively, internal ring path Electrically connect with outer shroud path.

Further, at input/output port impedance (Z₀) given under conditions of, be can determine that by following formula and derivation Second isolation resistance (R₂) resistance, the first isolation resistance (R₁) resistance, first order micro-strip impedance (Z₁) and the resistance of second level micro-strip Anti-(Z₂) value:

$Z_1^2=2Z_2^2;Z_o=\frac{\frac{2Z_2^2}{R_1}*\frac{R_2}{2}}{\frac{2Z_2^2}{R_1}+\frac{R_2}{2}}=\frac{2Z_2^2*R_2}{4Z_2^2+R_1{R}_2};R_1{R}_2=4Z_2^2.$

Further, at input/output port impedance (Z₀) under conditions of given 50 Ω, it may be determined that the second isolation resistance (R₂) Resistance be 200 Ω, the first isolation resistance (R₁) resistance be 90 Ω, first order micro-strip impedance (Z₁) 93 Ω and second level micro-strip Impedance (Z₂) value 67 Ω.

Further, in the case of isolation resistance determines, use the AppCAD computed in software co-planar waveguide pair of Agilent Answer the dimensional parameters of characteristic impedance.

Further, described concentric structure is concentric structure, or concentric rectangles structure or with one heart other shapes knot Structure；Described path live width is 3mm.

Further, described concentric structure is concentric structure, is connected to the concentric circular bunch of input port: from the concentric center of circle Being 9.37mm to internal ring path Mean radius, from concentric circular center to center, annulus path Mean radius is 14mm, from the concentric center of circle Being 18.63mm to outer shroud path Mean radius, the gap between concentric circular is 1.63mm；It is connected to the concentric circular of output port Bunch: being 10.14mm from the concentric center of circle to internal ring path Mean radius, from concentric circular center to center, annulus path Mean radius is 14mm, is 17mm from the concentric center of circle to outer shroud path Mean radius, and the gap between concentric circular is 0.86mm；The first order and second Isolation resistance between Ji is 90 Ω, and the second level is 200 Ω with the isolation resistance of outfan.

Further, described balun also includes one 180 ° added behind of one output port of power splitter Phase inverter so that two output ports of concentric structure power splitter have 180 ° of phase-shift characterisitcs.

According to a further aspect in the invention, it is provided that the method for designing of a kind of balun, described method includes Following steps:

Design a concentric structure co-planar waveguide power splitter, under conditions of input and output impedance is given, determine isolation electricity The resistance of resistance and the structural parameters of co-planar waveguide.

Further, described concentric structure co-planar waveguide power splitter uses two-stage cascade form, hinders at input/output port Under conditions of anti-given 50 Ω, it may be determined that the resistance of the second isolation resistance is 200 Ω, the resistance of the first isolation resistance is 80-100 Ω, value 67 Ω of first order micro-strip impedance 93 Ω and second level micro-strip impedance.

Further, described method for designing also comprises the steps:

Design a phase inverter, it is ensured that the resistance value at phase inverter two ends is stable so that two of concentric structure power splitter defeated Go out port and there are 180 ° of phase-shift characterisitcs.

The balun of the application present invention, available broader bandwidth, and be prone to measure whole S parameter.

Accompanying drawing explanation

In order to be illustrated more clearly that the technical scheme of the embodiment of the present invention, required use in embodiment being described below Accompanying drawing be briefly described, it should be apparent that, below describe in accompanying drawing be only some embodiments of the present invention, for this From the point of view of the those of ordinary skill of field, on the premise of not paying creative work, it is also possible to obtain other according to these accompanying drawings Accompanying drawing.

Fig. 1 is the schematic diagram of the balun through two-stage cascade of one embodiment of the invention.

Fig. 2 is the power splitter principle schematic of one embodiment of the invention.

Fig. 3 is based on Fig. 2 principle circuit theory schematic diagram in the case of even mode division analysis.

Fig. 4 is based on Fig. 2 principle circuit theory schematic diagram in the case of odd mode analysis.

Fig. 5 is the schematic diagram of the balun through a power splitter of another embodiment of the present invention.

Detailed description of the invention

Describe in more detail the exemplary embodiment of the present invention below with reference to accompanying drawings.Although accompanying drawing shows the present invention Exemplary embodiment, it being understood, however, that may be realized in various forms the present invention, and should be by embodiments set forth here Limited.On the contrary, it is provided that these embodiments are to enable the more thorough explanation present invention, and can be complete by the scope of the present invention Whole conveys to those skilled in the art.

Balun shown in Fig. 1, is the concentric power divider structure using two-stage cascade, including Wilkinson power splitter, co-planar waveguide (CPW) and 180 ° of phase inverters, this balun can test its whole S ginseng The microstrip balun of number.Concrete principle analysis is as follows:

1, Wilkinson power splitter

Have an advantage in that method for designing is relatively simple, be easily achieved, and when input/output port all mates, output port High isolation can be realized.For the Wilkinson power splitter of two-stage cascade structure, its schematic diagram is as in figure 2 it is shown, operating frequency For f, power splitter input and output impedance is 50 Ω, and is the reference impedance of circuit.The first order is respectively with second level micro-strip impedance Z₁, Z₂.Electrical length isIn the first order and the second level by connecting resistance R₁, R₂Realize isolation.Due to its structure It is centrosymmetric, this circuit can be analyzed with even odd mode theory.

(1) even mode division analysis

In the case of merit is divided, branch port 2 (Port2) and port 3 (Port3) signal amplitude of power splitter are equal, phase place phase With.Electric current is not had to flow through the plane of symmetry of circuit, resistance R₁, R₂It is considered as open circuit, can remove.Port diagnostic impedance is Z₀.Even mould electricity Road is analyzed as shown in Figure 3.

Owing to power splitter is symmetrical about centrage, therefore have only to individually analyze branch port 2 or port 3.In these feelings Under condition, the port voltage of the public port 1 of power splitter is constant, and port current reduces half, and characteristic impedance is equivalent to 2Z₀.By 2 Section characteristic impedance is respectively Z₁And Z₂1/4 wavelength impedance matched line by public port impedance 2Z₀Match branch port impedance Z₀。

Under operating frequency f, output port impedance is

$Z_{o1}=Z_1\frac{2Z_0+j*Z_1*tan\left(\mathrm{\β}l\right)}{Z_1+j*2Z_0*tan\left(\mathrm{\β}l\right)}=\frac{Z_1^2}{2Z_0}---\left(1\right)$

$Z_o=Z_2\frac{Z_{o1}+j*Z_2*tan\left(\mathrm{\β}l\right)}{Z_2+j*Z_{o1}*tan\left(\mathrm{\β}l\right)}=\frac{Z_2^2}{Z_{o1}}=\frac{Z_2^2}{\frac{Z_1^2}{2Z_0}}=\frac{2Z_0{Z}_2^2}{Z_1^2}---\left(2\right)$

Can obtain

$Z_1^2=2Z_2^2---\left(3\right)$

Therefore, if the characteristic impedance of matched line meet relational expression (3) just can be by branch port impedance and public port Impedance matching is good.

(2) odd mode analysis

In the case of strange mould, power splitter 2,3 port signal amplitudes are equal, but phase 180 °.Power splitter central plane is Zero potential, i.e. ground connection.Electricity power splitter strange moding circuit analysis chart is as shown in Figure 4.

Owing to centrage is zero potential surface, therefore public port equiva lent impedance is zero, is Z by characteristic impedance₁1/4 resistance At isolation resistance R after the conversion of anti-line₁Place is equivalent to open circuit, therefore isolation resistance R₁The impedance at placeMeet:

$Z_{o1}=\frac{R_1}{2}---\left(4\right)$

Z₀₁It is Z by characteristic impedance₂1/4 impedance line conversion after be,

$Z_{o2}=\frac{{Z_2}^2}{\frac{R_1}{2}}=\frac{2{Z_2}^2}{R_1}---\left(5\right)$

Z₀₂With isolation resistance R₂Branch port impedance Z is matched after parallel connection₀,

$Z_o=\frac{\frac{2Z_2^2}{R_1}*\frac{R_2}{2}}{\frac{2Z_2^2}{R_1}+\frac{R_2}{2}}=\frac{2Z_2^2*R_2}{4Z_2^2+R_1{R}_2}---\left(6\right)$

Simultaneously need to isolation resistance R₁And R₂The power of upper consumption is the most equal.The voltage assuming Port2 port is V.

Then R₂The power of upper consumption

$P_2=\frac{2V^2}{R_2}---\left(7\right)$

Isolation resistance R after 1/4 impedance line conversion is understood by transmission line theory₁On electric current be

$I_1=-j\frac{V}{Z_2}---\left(8\right)$

Then its power consumption is

$P_1=I_1^2\frac{R_1}{2}=\frac{2V^2{R}_1}{Z_2^2}---\left(9\right)$

Because P₁=P₂, by (7) formula, (9) Shi Ke get

$R_1{R}_2=4Z_2^2---\left(10\right)$

Formula (3), (6), (10) give the criterion that parameter selects, generally take port identity impedance Z₀=50 Ω. In order to reach in wider band limits, standing wave is smaller, and isolation is big, through certain choice, and will the substitution of (10) formula (6) Shi Ke get: R₂=4Z₀=200 Ω.Application AppCAD software emulation goes out R afterwards₁Approximation value be 90 Ω, thus release Z₁ =93 Ω, Z₂=67 Ω.

To sum up, following circuit parameter: Z is chosen₁=93 Ω, Z₂=67 Ω, R₁=90 Ω, R₂=200 Ω.

2, co-planar waveguide (CPW) structure

Co-planar waveguide CPW can support that Quasi-TEM mode is propagated.Compared with traditional microstrip line, have the advantage that and be prone to Processing, it is easy to the most various microwave devices, radiation loss are little.Co-planar waveguide is in wave filter, frequency mixer, phase shifter etc. In be widely used.

Use the dimensional parameters of the character pair impedance of AppCAD computed in software CPW of Agilent.HFSS uses finite element Method, can solve S parameter and the full-wave electromagnetic field of arbitrary shape three-dimensional passive structures easily and accurately.Use HFSS modeling imitative Very, then it is optimized, obtains preferable index.

This power splitter takes the form of two-stage cascade, constitutes especially by two concentric structure cascades, uses Rogers4350B is the co-planar waveguide of base material, and each concentric structure is the most successively by internal ring path, central trace and outer shroud Path forms, and internal ring path electrically connects with outer shroud path.In design, the live width of all paths is 3mm.As shown in table 1, it is connected to The concentric circular bunch of input port 1 (Port1): from the concentric center of circle to internal ring path Mean radius r11=9.37mm, from the concentric center of circle To central circular path Mean radius r12=14mm；From the concentric center of circle to outer shroud path Mean radius r13=18.63mm, with one heart Gap between circle is gap1=1.63mm.It is connected to the concentric circular bunch of output port: from the concentric center of circle to internal ring path midpoint Radius r11=10.14mm, from concentric circular center to center annulus path Mean radius r12=14mm；From the concentric center of circle to outer shroud rail Line Mean radius r13=17mm, the gap between concentric circular is gap2=0.86mm.Isolation electricity between the first order and the second level Resistance is R1=80-100 Ω, preferably 90 Ω, and the second level is R2=200 Ω with the isolation resistance of outfan.

Parameter	Value	Parameter	Value
				r11	9.37mm	r21	10.14mm
r12	14mm	r22	14mm
				r13	18.63mm	r23	17mm
gap1	1.63mm	gap2	0.86mm
				R1	90Ω,80-100Ω	R2	200Ω

Table 1

The present invention use the balun output port of two-stage cascade structure can realize more than 20dB every It it is ± 5 ° from the phase contrast spent in frequency range used.Balun designed by the present invention can pass through vector net Network analyser accurately records its whole S parameter, and then in the circuit needing accurate S parameter.Such as can calculate grinding of antenna In studying carefully, need accurately to understand the S parameter of balun, then carry it into simulation result, and then compare the imitative of the antenna containing balun Gap between true value and actual measured value.

3, phase inverter

In order to realize inverter functionality, at the phase inverter of one 180 ° added behind of power splitter, owing to using co-planar waveguide, then Only its ground wire and holding wire need to be overturned.Its microstrip structure is two-stage circular topology structure, and circular configuration can reduce this Coupling between level microstrip line and interstage coupling, do not have the most discontinuous problem of rectangular configuration simultaneously, and two-stage circle opened up Flutter structure and add bandwidth.

Present invention can apply to the fields such as field of electromagnetic compatibility, microwave circuit field, Antenna Design, it is provided that one has height The balun method for designing of isolation, covers the wideband microband balun of 1GHz-2GHz frequency range, and can pass through Network is analyzed in right amount and is accurately recorded its whole S parameter (balancing device hybrid guided mode scattering parameter), and then can be used for needing accurate S to join In the circuit of number, such as can be used in the research of calculating antenna, need accurately to understand the S parameter of balun, then carry it into imitative True result, compares the difference between simulation value and the actual measured value of the antenna containing balun.

Based on above-mentioned principle, an alternative embodiment of the invention is to use one-level power splitter, i.e. only with a concentric merit Divide device structure, so can obtain the balun of compact.The coplanar ripple using Rogers 4350B to be base material Leading, each concentric structure is made up of internal ring path, central trace and outer shroud path the most successively, internal ring path and outer shroud rail Line electrically connects.In design, the live width of all paths is 3mm.As shown in table 2, the concentric circular bunch of input port it is connected to: from one heart The center of circle is to internal ring path Mean radius r11=10.22mm, from concentric circular center to center annulus path Mean radius r12=14mm； From the concentric center of circle to outer shroud path Mean radius r13=17.78mm, the gap between concentric circular is gap=0.78mm, input Gap between Kou and the gap between output port are gapr=0.2mm, and isolation resistance is R=100 Ω.

Parameter	Value
		r11	10.22mm
r12	14mm
		r13	17.78mm
gap	0.78mm
		gapr	0.2mm
R	100Ω

Table 2

Based on above-mentioned principle, the present invention also provides for the method for designing of a kind of balun, and described method includes Following steps:

Design a concentric structure co-planar waveguide power splitter, under conditions of input and output impedance is given, determine isolation electricity The resistance of resistance and the structural parameters of co-planar waveguide.Concrete:

One embodiment is, the co-planar waveguide power splitter of one two-stage cascade structure of design.As it is shown in figure 1, cascade structure Power splitter uses two-stage cascade form, in order to improve the isolation of output port, in input/output port impedance Z₀Given bar Under part, can determine that the second isolation resistance R by formula (3), (6), (10) and derivation₂Resistance, i.e. R₂=4Z₀, soft by emulation Part is counter releases the first isolation resistance R₁Resistance, and then obtain first order micro-strip impedance Z₁With second level micro-strip impedance Z₂Value.

Such as, input and output impedance is Z₀In the case of=50 Ω, obtain:

Z₁=93 Ω, Z₂=67 Ω, R₁=90 Ω, R₂=200 Ω.

Further, concentric structure power splitter can use concentric structure as depicted, it would however also be possible to employ concentric rectangles Or other shape and structures with one heart.

Another embodiment is, the co-planar waveguide power splitter of one one-level cascade structure of design.As it is shown in figure 5, only with One concentric power divider structure, can obtain the balun of compact.

Further, concentric structure power splitter can use concentric structure as depicted, it would however also be possible to employ concentric rectangles Or other shape and structures with one heart.

As the further improvement of above-mentioned several embodiments, the method for designing of a kind of balun also include as Lower step:

Design a phase inverter, it is ensured that the resistance value at phase inverter two ends is stable so that two of concentric structure power splitter defeated Go out port and there are 180 ° of phase-shift characterisitcs.

The balun of the application present invention, available broader bandwidth, and be prone to measure whole S parameter, In wider frequency band range, do not only have preferable port isolation characteristic, the most comparatively ideal phase characteristic simultaneously.

Each embodiment in this specification all uses the mode gone forward one by one to describe, identical similar portion between each embodiment Dividing and see mutually, what each embodiment stressed is the difference with other embodiments.Especially for device or For system embodiment, owing to it is substantially similar to embodiment of the method, so describing fairly simple, relevant part sees method The part of embodiment illustrates.Apparatus and system embodiment described above is only schematically, wherein said conduct The unit of separating component explanation can be or may not be physically separate, the parts shown as unit can be or Person may not be physical location, i.e. may be located at a place, or can also be distributed on multiple NE.Can root Factually border need select some or all of module therein to realize the purpose of the present embodiment scheme.Ordinary skill Personnel, in the case of not paying creative work, are i.e. appreciated that and implement.

Those skilled in the art be appreciated that module each in embodiment can be carried out adaptivity change and They are arranged in one or more equipment different from this embodiment.Unless otherwise being expressly recited, disclosed in this specification Each feature can be replaced by providing identical, equivalent or the alternative features of similar purpose.

The foregoing is only the preferred embodiments of the invention, be not limited to the claims of the present invention. The most described above, for those skilled in the technology concerned it would be appreciated that and implement, therefore other are based on institute of the present invention The equivalent that disclosure is completed changes, and should be included in the covering scope of the claims.

Claims (10)

1. a balun, including concentric structure co-planar waveguide power splitter, it is characterised in that: described power splitter is adopted Use two-stage cascade form, by two concentric structures, with Rogers 4350B as base material co-planar waveguide cascade form, Mei Getong Core structure is made up of internal ring path, central trace and outer shroud path the most successively, and internal ring path electrically connects with outer shroud path.

Balun the most according to claim 1, it is characterised in that: at input/output port impedance (Z₀) give Under conditions of Ding, can determine that the second isolation resistance (R by following formula and derivation₂) resistance, the first isolation resistance (R₁) resistance Value, first order micro-strip impedance (Z₁) and second level micro-strip impedance (Z₂) value:

$Z_1^2=2Z_2^2;Z_O=\frac{\frac{2Z_2^2}{R_1}*\frac{R_2}{2}}{\frac{2Z_2^2}{R_1}+\frac{R_2}{2}}=\frac{2Z_2^2*R_2}{4Z_2^2+R_1{R}_2};R_1{R}_2=4Z_2^2.$

Balun the most according to claim 2, it is characterised in that: at input/output port impedance (Z₀) give Under conditions of fixed 50 Ω, it may be determined that the second isolation resistance (R₂) resistance be 200 Ω, the first isolation resistance (R₁) resistance be 90 Ω, first order micro-strip impedance (Z₁) 93 Ω and second level micro-strip impedance (Z₂) value 67 Ω.

Balun the most according to claim 1, it is characterised in that: in the case of isolation resistance determines, Use the dimensional parameters of the AppCAD computed in software co-planar waveguide character pair impedance of Agilent.

Balun the most according to claim 4, it is characterised in that: described concentric structure is concentric circular knot Structure, or concentric rectangles structure or other shape and structures with one heart；Described path live width is 3mm.

Balun the most according to claim 4, it is characterised in that: described concentric structure is concentric circular knot Structure, is connected to the concentric circular bunch of input port: from the concentric center of circle to internal ring path Mean radius be 9.37mm, from the concentric center of circle to Central circular path Mean radius is 14mm, from the concentric center of circle to outer shroud path Mean radius be 18.63mm, between concentric circular Gap is 1.63mm；Be connected to the concentric circular bunch of output port: from the concentric center of circle to internal ring path Mean radius be 10.14mm, From concentric circular center to center, annulus path Mean radius is 14mm, from the concentric center of circle to outer shroud path Mean radius be 17mm, with Gap between heart circle is 0.86mm；Isolation resistance between the first order and the second level is 90 Ω, the second level and outfan every It is 200 Ω from resistance.

Balun the most according to claim 1, it is characterised in that: described balun also wraps Include the phase inverter of one 180 ° added behind of one output port of power splitter so that two output ports of concentric structure power splitter There are 180 ° of phase-shift characterisitcs.

8. a method for designing for balun, described method comprises the steps:

Design a concentric structure co-planar waveguide power splitter, under conditions of input and output impedance is given, determine isolation resistance Resistance and the structural parameters of co-planar waveguide.

Balun the most according to claim 8, it is characterised in that: described concentric structure co-planar waveguide merit is divided Device uses two-stage cascade form, under conditions of input/output port impedance gives 50 Ω, it may be determined that the resistance of the second isolation resistance Value is 200 Ω, the resistance of the first isolation resistance is 80-100 Ω, first order micro-strip impedance 93 Ω and the value of second level micro-strip impedance 67Ω。

Balun the most according to claim 8, it is characterised in that: described method for designing also includes as follows Step:

Design a phase inverter, it is ensured that the resistance value at phase inverter two ends is stable so that two outfans of concentric structure power splitter Mouth has 180 ° of phase-shift characterisitcs.